Repairing Signallab BMS

[Degull]

After doing some reading on the forum it looks like I have a 16S V2.5 Signallab BMS with problems. The BMS was a give me with a battery that I purchased from a forum member. I made my own A123 48V battery from recycled Dewalt packs. I've checked all the sense wire connections and they are hooked in the correct order. The B- connection hooked to the battery negative. I'm measuring voltage across the P- connection and the battery positive. For some reason the output of the BMS is only 40V but the pack voltage is sitting at 53V. I plan on removing and testing the mosfets but I have no idea what the part numbers of the mosfets are. The markings on the mosfets have been sanded off.
I tried charging the pack as well and it does not seem to be doing anything. All the leds stay off. I'll get some pictures up later.

[dnmun]

one 'l'.

if it will not take a charge, make sure all the sense wires are in the right order. if they are reversed now, and connected to the cells, it could already be toast. you can look for the voltage on the gate of the charging FET to see if it is turned on.

[Degull]

Here is a quick picture of the sense wires from the battery. I have to go out, but I will hook everything back up and measure the charging fet's gate voltage when I get back.

[Degull]

I measured between the charger negative input (C- pad). The gate voltage is reading 1.6V, the drain is 8.5V and 0V on the source leg.

The mosfets have the part numbers sanded off. I have some extra 4110 mosfets, any chance I can use the 4110? I haven't desoldered them yet.

[DAND214]

The 4110 will work. Ping said they were fine.

Have you tested between B- and the last red balance lead. I think that is how it's done. Been a while for me to look at a BMS. LiPo's don't have them normaly.

Dan

[dnmun]

i think you measured the gate at 8.5V so it should charge up if you connect the charger. doesn't look like anything is wrong. i see no need to replace the output mosfets.

[Degull]

All the readings were measured with the negative lead of my DMM on the charger negative (C-) pad. The charger was hooked up with the positive lead going to the positive on the battery and the negative lead to the C- pad. The charger was providing 60V. The drain or the body of the mosfets are all soldered together and measured 8.5V.
The charge mosfet is the one at the very top of the picture. The first leg of the first mosfet, starting from the top of the picture is the gate which I measured 1.6V.

[Degull]

I replaced all the mosfets and no joy. There is still no output between the battery positive and the BMS P- connection. Also the charging does not seem to be doing anything. I found an open trace on the back side of the board. Looks like the BMS suffered some kind of short circuit. I soldered in a jumper wire to fix the open trace but still no joy!
I measured the gate voltage of the output mosfets and there is no voltage there. The gates of the mosfets are fed by a 14 pin smd IC. The 14 pin IC's part number has been sanded off so I do not know what to look for other than there is 12V between pin 7 and 14. Anyone know what this part is?

[dnmun]

what is the voltage on the gate if you put the black lead of the voltmeter on the battery negative? did you replace that one too? i don't think there was anything wrong with any of them from looking at the picture.

[Degull]

I replaced all the mosfets. The gate voltage with the negative lead of the voltmeter on battery negative is 2.5V

I've emailed Ping and asked if he could help in identifying the 14 pin IC. Thanks for the help!

[dnmun]

if the gate reads that low then it is not getting the full voltage of the first 3 cells as it should. what is the voltage on each of the first three cells? the black sense wire is the top of #1. measure over to the B- spot from the top of #1,2,3. the C_ spot doesn't serve as ground for the BMS.

there is nothing wrong with the 14 pin comparator. why did you think there was a missing trace on the pcb?

[Degull]

Starting from the black sense wire, #1 is 3.3v, #2 6.6V and #3 10V.

I noticed the trace was burnt because there was a burn in one small spot. I did not notice before because the board is black and it is a very small via. The trace was open circuit.

[dnmun]

ok that is in the opto chain that drives the gate of the charging FET. if it got shorted, that may have damaged the optos, but i don't know optos so i cannot tell you more than that.

the via is in the adjacent trace, not the one you put the wire on. what is the voltage on that via? the wire should be at ground. imo